Saturday, July 30, 2016

A Brief History of the Soviet Space Shuttle Buran, Part One: Guest Post by Jay Chladek

Occasionally
this blog features writing by other space historians and figures.
During the next two weeks, I am proud and honored to present a
history of the Soviet Buran space shuttle by someone who knows an
awful lot about it. Here's
the dirt on everybody's favorite shuttle, by space historian Jay
Chladek:

A Brief History
of Soviet Space Shuttle Buran, Part
One (CLICK FOR MORE AFTER THE JUMP!)

It
has been said that imitation is a form of flattery. During the Cold
War between the United States and the Soviet Union from the late
1940s until the beginning of the 1990s, there was a bit of what one
could describe as industrial espionage going on between these two
countries which would ultimately end up becoming global superpowers.
The two most visible aspects of that were the Tu-95 (NATO codename
"Bull") bomber, a copy of the Boeing B-29 Superfortress
reverse engineered from captured airframes and the nemesis of the
Korean war, the MiG-15 powered by a copy of the Rolls Royce Nein jet
engine.

During
the early days of the space race, it was felt that the Soviets might
also be copying American spacecraft and rocket designs as well. But
over time it was revealed that this was not the case. The R-7 rocket,
along with the Vostok, Voskhod and Soyuz spacecraft were completely
original and the Soviets took great pride in their achievements. So
when pictures of what apparently looked like a nearly identical copy
of NASA's space shuttle were seen sitting on a launch pad at the
Baikonur Cosmodrome in 1988, it was greeted by the Western press with
a combination of excitement, bewilderment and concern. Had the Soviet
Union really copied the most technically complex manned space vehicle
ever built? If so, why?

The Seeds of Buran

For
an answer to that, we have to go back to the early 1970s. As we know
today, but was a closely guarded secret at the time, the Soviets were
working on a lunar program in the form of the N1 moon rocket, and
things were not going well. A bit of sideways thinking got the first
civilian space station, "Salyut," off the ground, but it
was not the brain child of Vasili Mishin, the head of Sergei
Korolev's old bureau and he resented it. Ultimately when the fourth
N1 launch attempt ended in failure, it took some extreme arm twisting
by Defense Minister Dimitri Ustinov to get Mishin to fall in line and
focus on developing Salyut.

As time went on, Salyut would mature and
ultimately develop into a very successful series of stations. But at
the time the decision was made, no one knew how successful it would
be. Even with Mishin agreeing to back Salyut, higher ups in Soviet
government decided that Mishin was not the long term answer for
Korolev's bureau and ultimately replaced him with Valentin Glushko, a
rival designer with his own bureau that focused on the development of
rocket engines.

From Wikimedia Commons: "OK-GLI Buran programme spacecraft at the Technik Museum Speyer, Germany on exhibition during 2013." Image taken from Flickr user pasukaru76's photostream, marked as CC0 1.0. (public domain) by its author.

During the 1960s, Korolev despised
Glushko, but had to work with him as Korolev needed Glushko's rocket
engine designs to power his firm's own missiles and rockets. It
really came to a head with the N1 as Korolev felt that Glushko was
stonewalling on the development of engines that used cryogenic fuels
(liquid hydrogen), such as the H-1 and J-2 motors used to power the
upper stages of the Saturn boosters. Glushko favored engines powered
by kerosene and liquid oxygen (LOX) or hypergolics.

They were easier
to develop and in the case of hypergolic fuels, they didn't require
refrigeration equipment to prevent them from boiling off. Liquid
hydrogen (LHX) is a much more powerful fuel, but it required much
more extreme refrigeration than LOX as its liquid state is only about
20 degrees above absolute zero. Gaseous hydrogen's small atomic size
also requires special handling and materials to keep it from leeching
out compared to oxygen or nitrogen. Even with proper equipment and
the best refrigeration, liquid hydrogen is still prone to boiling off
at a rate of about 1% a day. Worse than that though, liquid hydrogen
had been known to combust on contact with almost anything if there is
an oxidizer present. Hence the difficulty with taming it for use in
rocket engines.

Ultimately Korolev went with less
efficient motors from a different design firm and many believe this
is a key contributor as to why the N1 rocket failed to send a payload
into orbit, let alone the moon. The engines were a sound design, but
having to cluster 30 of them in the first stage and almost as many in
the second stage meant the chances for failure were amplified many
times compared to the much smaller number of motors in the Saturn V.
By comparison, the S-II stage of the Saturn V used five LHX/LOX
powered J-2 motors.

When
Glushko took over Korolev's bureau in 1974, he decided to merge the
two design firms into one, renaming it NPO Energia. Even though
memories of Korolev and Glushko's feud were still relatively fresh,
many engineers at Energia considered this move a good one as the new
firm had a strong hand which many felt it lacked under Mishin. But
now the question became what to do with a firm this massive. For
that, the Soviets looked to what the Americans were doing.

The Decision

Congress
had approved NASA's plan to develop a reusable space shuttle in early
1972 and by 1974, the agency had settled on a vehicle with a winged
orbiter, solid rocket boosters and a huge external fuel tank housing
fuel and oxidizer to power the orbiter's LHX/LOX engines. The vehicle
had the potential to deliver some very large payloads into Earth
orbit and in order for NASA to proceed with development, they needed
backing from the United States Air Force and the Department of
Defense. While NASA planned to fly the vehicle from Cape Canaveral,
the Air Force put plans into motion to launch the shuttle into polar
orbits from their facility at Vandenberg Air Force Base in
California. Polar orbits are ideal for reconnaissance of the Soviet
Union due to how far north it is located, but what concerned the
Soviets greatly is the same polar orbits could also be used for
attack as well.

When the space shuttle was designed, the
USAF had a requirement for a 1,500 mile cross range capability,
meaning a returning orbiter could land at a runway up to 1,500 miles
to either side of its orbit track. By comparison, space capsules
don't have very much cross range. If NASA were the only user of the
space shuttle, a lifting body vehicle based on the X-24 would have
been ideal. But polar orbit launches need a higher cross range if a
problem develops. As the Earth rotates under a spacecraft in orbit,
the orbit track shifts west. Orbits with a lower inclination (the
angle of the orbit relative to the equator of the Earth) are easier
to return from if the vehicle has to make a pinpoint landing at a
specific place, such as its launch site. The shuttle's cross range
requirement was needed to allow for a shuttle to land at Vandenberg
after only one polar orbit, usually if an emergency required a
shuttle to return right away. But, it also meant that the USAF could
theoretically launch, deploy a payload and land before anyone in the
Soviet Union would know what was going on and such a payload might be
an offensive weapon rather than a simple reconnaissance satellite.

In
the 1970s, the Soviet intelligence and military agencies were very
paranoid by Western standards. Just to give you some idea of how
paranoid they were, the Soviet Almaz military space station, which in
modified form became the basis of the civilian Salyut station
program, was equipped with a 23 mm automatic cannon as a
defense against any prying U.S. spacecraft that might want to take an
up close look. The weapon thankfully was never utilized in anger, but
it was test fired in orbit and showed just to what lengths the
Soviets were willing to protect their assets because of a perceived
threat.

So when the design specifications for the shuttle
were published, the Soviet military looked at them with great concern
and decided they needed a similar capability. While they didn't know
exactly what the USAF were planning to do with the space shuttle, the
Soviet military figured it must be important enough that they should
have their own shuttle type vehicle and they should start work as
soon as possible since the Americans already had a head start on
them. So the Soviet military made the decision to require development
of their own MKS (Soviet acronym for "Reusable Space System")
in June, 1974 and NPO Energia was given responsibility for it in
October of that year.

Rocket Booster Development

Remember
how I said Glushko was reluctant to develop rocket engines which
utilized cryogenic fuels? While Apollo had made use of LHX for the
second and third stages of the Saturn V rocket, NASA was planning to
use it to power the orbiter the entire way from launch to orbit and
make those engines re-useable. The shuttle was also designed to make
use of two very large solid rocket boosters to give it the added
thrust it required and the Soviets had no equivalent capability.

With
Glushko merging his bureau with Korolev's old one, he decided to
focus it on developing a new rocket booster powered by LHX/LOX
engines. Unlike shuttle, this new rocket wouldn't be intended
exclusively for use with the new space plane. Instead it could be
used to launch several different payloads into orbit and perhaps the
moon or other planets. At the time, the Soviets had a heavy lift
booster in the form of the Proton rocket. But Proton was developed by
a different design bureau, not Korolev's and Glushko must have felt
the need to eclipse his rivals now that he had the full resources of
what were once two design bureaus. On paper, this new booster would
make Proton look relatively puny. This new booster design was
originally called "Vulkan".

Looking at Vulkan's
core, it looks very much like a space shuttle external tank with four
rocket engines strapped to the bottom. Additional power would be
provided by strap-on rocket stages powered by RD-170 engines fueled
by LOX and Kerosene as an alternative to the SRBs of NASA's space
shuttle. For use with the Soviet shuttle, four boosters were needed,
but the core rocket could be powered by anywhere from two to eight
boosters depending on the size and weight of the payload that needed
to be flown. The engines of the Vulkan, designated RD-0120, were
about the same size and power class as the SSMEs used in shuttle, but
the Soviets weren't concerned with making them reusable. The engines
were also capable of being throttled and represented a leap in Soviet
rocket design technology. Development was long and difficult, but the
first production rocket motors were ready for flight by 1987.

Soviet Shuttle Development

So
why does the Soviet shuttle look so much like the American one? The
answer is aerodynamics, although there is a bit of that Soviet
industrial espionage hiding under the surface. By the time NASA
settled on the final shape of their orbiter, they had undergone
hundreds of hours of wind tunnel testing and simulation to work out
as many bugs in the design as possible. The shuttle's double-delta
wings were needed for its cross range capability. Technically, given
the massive size of the Soviet Union, they probably could have gone
with a design that had less cross-range, but at the time there were
no launch and support facilities as large as Baikonur to the east or
west of it.

In
a spacecraft system as complex as a shuttle, the shape is only the
start though and the Soviets had a lot of catching up to do and come
up with their own solutions to problems not encountered with the
American shuttle. It took five years of development before the
designers settled on a shape that very much was a mirror of the space
shuttle, but with differences. For one thing, since the Soviet design
lacked SSMEs, its rear end contained only the orbital maneuvering
engines and due to the change in the shuttle's center of gravity, the
nose gear was moved further back from the nose into the belly. Even
with these changes, the basic dimensions of the Soviet shuttle were
about the same, although the shapes appeared a bit cruder in
spots.

The shape was settled on in 1980 and to test the
design, the Soviets began building several test airframes for both
structural and flight testing in much the same way that the Americans
built STA-99 (which became Challenger) and OV-101 Enterprise.
Instead of developing an aircraft to piggy-back the shuttle to
altitude for glide testing, the Soviets instead powered one of their
test airframes with four turbojet engines. This orbiter became the
OK-GLI test vehicle and it made 25 flights from 1985 to early 1988.
The Antonov AN-225 cargo plane was developed with the capability to
transport the shuttle. But it wasn't finished until 1988. Prior to
that, shuttle airframes and portions of the rocket stages were
transported on the backs of specially modified M-4 Bison bombers. But
the shuttle airframes were stripped-down and unfinished as a fully
completed shuttle was too heavy for air transport by an M-4.

Preparations For Flight

Even
with a relatively high priority dedicated to the shuttle program, the
Soviets had a long and difficult road getting it ready for flight. By
the mid-1980s, the orbiter, the rocket booster and the launch
facilities had fallen behind schedule. So additional money was
allocated and a crash program was undertaken to get everything ready.
Manpower on the orbiter, rocket booster and launch pad was increased
many times over to finish the vehicle.

In
an interesting parallel to NASA's shuttle, the preparation facilities
and launch pad for Buran was converted from one used to launch the
N-1 moon rocket. So final assembly took place in a massive hangar
which once housed parts for the Soviet lunar program. When assembled,
the stack would be transported to the pad horizontally on the same
transporter and dual railroad lines used to carry the N-1 as well and
it would be rotated to a vertical orientation at the pad.

As
with America's shuttle, development of the booster's rocket engines
and the heat resistant tiles were the two items that took the longest
time to refine and install. Some short cuts also took place as the
rocket booster first flew without any major testing of the full stack
on the ground. The first launch in 1987 sent up a payload called
"Polyus" which was a test bed of technology related to the
Soviets answer to Ronald Reagan's Strategic Defense Initiative. The
booster worked perfectly, but the payload failed to enter orbit as it
instead commanded itself to deorbit rather than boost itself into a
higher orbit. With the successful test of the rocket, all that was
needed was the orbiter.

*****

Stay tuned for part two of the Buran saga next week.

Jay
Chladek is a
freelance space historian and model builder who has written chapters
in various books about plastic models of aircraft and spacecraft,
both real and fictional. He
has
also won awards at various levels for his
model building work, and
has had
an interest in space since he
was a child
growing up in the 1970s. Outposts
on the Frontier: A Fifty Year History of Space Stationsis
his first book in the subject of space history, and will be published
as part of the University of Nebraska’s Outward Odyssey series in
2017.